1. Field of Invention
The invention relates to a hydraulic control apparatus for automatic transmissions provided with a lockup clutch-carrying hydraulic transmission unit, and more particularly to techniques for rendering a hydraulic control apparatus adaptable to variations in types of hydraulic transmission unit.
2. Description of Related Art
A torque converter or a fluid joint, as a hydraulic transmission unit provided on an automatic transmission, is usually provided with a lockup clutch for the purpose of reducing the transmission loss ascribed to a slip of a fluid.
The lockup clutches include a single plate-type lockup clutch (refer to, for example, Japanese Patent Laid-Open No. 71591/1995) having a comparatively small transfer torque but advantages residing in the light weight and compactness, and a multiplate-type lockup clutch (refer to, for example, Japanese Patent Registration No. 2641419) having large dimensions as compared with a single plate-type lockup clutch but a large transfer torque and excellent controllability.
The single plate-type lockup clutch employs the following structure. In such a lockup clutch, a clutch made integral with a clutch piston is operated in accordance with relative levels of hydraulic pressure in a converter chamber, as a hydraulic transmission chamber in a space between a transmission case and clutch plate, i.e. a differential pressure applied to the clutch plate. When a hydraulic pressure is supplied to the converter chamber, the clutch plate is press-engaged with the transmission case, and placed in a locked-up state (hereinafter referred to as xe2x80x9clockup onxe2x80x9d). Conversely, when a hydraulic pressure is supplied from a space between the transmission case and clutch plate, a lockup disengaged state (hereinafter referred to as xe2x80x9clockup offxe2x80x9d) is attained. Therefore, a hydraulic lockup chamber is opened with respect to the converter chamber.
On the other hand, the multiplate lockup clutch employs a structure in which a clutch piston and its engageable element are formed separately with a transmission case constituted by a clutch cylinder. Therefore, a hydraulic lockup chamber is formed independently of a converter chamber. In contrast with the case of the single plate-type lockup clutch, a space between the transmission case and a clutch piston constitutes the hydraulic lockup chamber, into which a high hydraulic pressure is supplied from the converter chamber to attain a locked-up state.
Changing the general structure of an automatic transmission every time, in order to adapt the automatic transmission to minute specification differences concerning the kind of vehicle and engine torque characteristics, causes manufacturing costs to increase greatly and lacks rationality. In general, in an automatic transmission, the control of a hydraulic transmission unit, including the control of a speed change gear and a lockup control operation, is done by a common hydraulic control apparatus, which is formed of a hydraulic circuit in which a large number of valves and orifices incorporated in a valve body are connected together by entangled oil passages. Therefore, the speed change gear can be adapted to various kinds of specifications by merely replacing some parts thereof with others. However, in a case where a hydraulic transmission unit of a different type of lockup clutch is used, the supply of a hydraulic pressure and a lockup operation with respect thereto are reversed as mentioned above. Consequently, the changing of the hydraulic circuit in accordance with the changed specifications cannot be done by simple part-changing work including the replacement of valves, so that a valve body as a whole is necessarily changed. The changing of a valve body causes an increase in the metal mold design expense for the production of the valve body, and the cost of manufacturing the apparatus increases.
To be more exact, a pressure regulating valve inserted in the hydraulic circuit for carrying out a lockup control operation is operated by a signal pressure applied thereto. When the occurrence of a failure to apply a signal pressure to the valve is imagined, attaining lockup off at the time of occurrence of a failure to output a signal pressure is important for securing the travel of a vehicle. In view of the matter, it is desirable irrespective of the type of lockup clutch in use that the applying of a signal pressure to the pressure regulating valve starts its pressure regulating operation. Due to the relationship between such an operation of the pressure regulating valve and the connection of oil passages to a hydraulic lockup chamber, it is impossible to adapt the hydraulic circuit to changed specifications by replacing a pressure regulating valve.
The invention has been made in view of the above circumstances, and provides a hydraulic control apparatus for automatic transmissions, capable of being adapted to a change in the specifications of a lockup clutch, in which the relationship between the supplying and discharging of a hydraulic pressure for a lockup operation is reversed with respect to the connection of the oil passages, without requiring substantial changes in a valve body, and, moreover, without changing the operation of a pressure regulating valve with respect to the application of a signal pressure.
According to one aspect of the invention, the hydraulic control apparatus for automatic transmissions provided with a hydraulic transmission unit in which a hydraulic lockup chamber of a lockup clutch is independent of a hydraulic transmission chamber, has a valve body which is formed by laminating at least two members and which has a pressure regulating valve adapted to regulate a hydraulic pressure supplied to the lockup clutch, a control unit adapted to apply a signal pressure to the pressure regulating valve, a source pressure oil passage adapted to supply a basic pressure for the above-mentioned hydraulic pressure regulating operation, and drain oil passages communicating with a drain port, the pressure regulating valve having a second port to which a signal pressure from the control unit is applied, a fourth port communicated with the hydraulic lockup chamber, a third port provided on one side of the fourth port, and a fifth port provided on the other side of the fourth port, an opening of an oil passage communicated with the third port and provided in one member of the valve body being formed so as to overlap both an opening of the source pressure oil passage and that of the drain oil passage which are provided in the other member of the valve body, an opening of an oil passage communicated with a fifth port and provided in the first-mentioned member of the valve body being formed so as to overlap both an opening of the source pressure oil passage and that of the drain oil passage which are provided in the second-mentioned member of the valve body, a separator plate provided with communication ports for communicating an opening of an oil passage, which is communicated with the third port, and that of the source pressure oil passage with each other, and an opening of an oil passage, which is communicated with the fifth port, and that of the drain oil passage with each other, being inserted between the two members of the valve body.
According to another aspect of the invention, the hydraulic control apparatus for automatic transmissions provided with a hydraulic transmission unit in which a hydraulic lockup chamber of a lockup clutch is opened in a hydraulic transmission chamber has a valve body which is formed by laminating at least two members on each other, and which has a pressure regulating valve adapted to regulate a hydraulic pressure supplied to the lockup clutch, a control unit adapted to apply a signal pressure to the pressure regulating valve, a source pressure oil passage adapted to supply a basic pressure for the above-mentioned hydraulic pressure regulating operation, and drain oil passages communicating with a drain port, the pressure regulating valve having a second port to which a signal pressure from the control unit is applied, a fourth port communicated with the hydraulic lockup chamber, a third port provided on one side of the fourth port, and a fifth port provided on the other side of the fourth port, an opening of an oil passage communicated with the third port and provided in one member of the valve body being formed so as to overlap both an opening of the source pressure oil passage and that of the drain oil passage which are provided in the other member of the valve body, an opening of an oil passage communicated with a fifth port and provided in the first-mentioned member of the valve body being formed so as to overlap both an opening of the source pressure oil passage and that of the drain oil passage which are provided in the second-mentioned member of the valve body, a separator plate provided with communication ports which communicate an opening of the oil passage, which is communicated with the third port, and that of the drain oil passage with each other, and an opening of an oil passage, which is communicated with the fifth port, and that of the source pressure oil passage with each other, respectively, being inserted between the two members of the valve body.
According to still another aspect of the invention, the hydraulic control apparatus for automatic transmissions provided with the hydraulic transmission unit in which the hydraulic lockup chamber of the lockup clutch is independent of the hydraulic transmission chamber has the pressure regulating valve further having first and sixth ports, the first port being provided on the opposite side of the sixth port to which side the regulating valve is moved when a signal pressure is applied from the control unit, an opening of a transmission chamber oil passage communicated with the hydraulic transmission chamber and that of a hydraulic lockup passage communicated with the hydraulic lockup chamber being provided in the second-mentioned member of the valve body, an opening of an oil passage communicated with the first port and that of an oil passage communicated with the sixth port being provided so as to overlap both an opening of a hydraulic transmission passage and that of a hydraulic lockup passage respectively, the separator plate having communication ports which communicate the oil passage, which is communicates with the first port, and the hydraulic transmission passage with each other, and the oil passage, which communicates with the sixth port, and the hydraulic lockup passage with each other respectively, whereby an effective structure is obtained.
According to a further aspect of the invention, the hydraulic control apparatus for automatic transmissions provided with the hydraulic transmission unit in which the hydraulic lockup chamber of the lockup clutch is opened in the hydraulic transmission chamber has the pressure regulating valve further having first and sixth ports, the first port being provided on the opposite side of the sixth port to which side the regulating valve is moved when a signal pressure is applied from the control unit, the hydraulic transmission passage communicated with the hydraulic transmission chamber and the opening of the hydraulic lockup passage communicated with the hydraulic lockup chamber being provided in the second-mentioned member of the valve body, an opening of an oil passage communicated with the first port and provided in the first-mentioned member of the valve body being provided so as to overlap both an opening of the hydraulic transmission passage provided in the second-mentioned member of the valve body and that of the hydraulic lockup passage, an opening of an oil passage communicated with the sixth port and provided in the first-mentioned member of the valve body being provided so as to overlap both an opening of the hydraulic transmission passage provided in the second-mentioned valve body and that of the hydraulic lockup passage, the separator plate having communication ports which communicate the oil passage, which communicates with the first port, and the hydraulic transmission passage with each other, and the oil passage, which communicates with the sixth port, and the hydraulic lockup passage with each other respectively, whereby an effective structure is obtained.
According to another aspect of the invention, the hydraulic control apparatus for automatic transmissions includes a relay valve having a port to which a signal pressure from the control unit is applied and a port in communication with the hydraulic transmission chamber, the relay valve adapted to control a hydraulic pressure in the hydraulic transmission chamber in accordance with the signal pressure from the control unit, whereby an effective structure is obtained.
According to still another aspect of the invention, the hydraulic control apparatus for automatic transmissions has the relay valve formed separately from the pressure regulating valve, whereby an effective structure is obtained.
According to a further aspect of the invention, the hydraulic control apparatus for automatic transmissions has the relay valve made integral with the pressure regulating valve, whereby an effective structure is also obtained.
In the first structure, the opening of the oil passage in communication with the third port of the pressure regulating valve and that of the oil passage in communication with the fifth port thereof which are provided in one member of the valve body are provided so as to overlap both the opening of the source pressure oil passage and that of the drain oil passage which are provided in the other member of the valve body respectively. Therefore, when a hydraulic transmission unit in which the hydraulic lockup chamber is independent of the hydraulic transmission chamber is changed to a hydraulic transmission unit in which the hydraulic lockup chamber is opened in the hydraulic transmission chamber, it is possible, by merely replacing a separator plate inserted between the two members of the valve body, to reverse the relationship between the supplying and discharging of a hydraulic pressure done by an operation of the pressure regulating valve, and thereby adapt the apparatus to a change in the type of a lockup clutch of the hydraulic transmission unit. Consequently, according to this structure, only the replacement of a separator plate, which serves the purpose by merely making a change of the position of the communication port thereof, removes the need to replace the valve body, which demands a change of the design of a metal mold therefor, when the arrangement of the oil passages is changed.
In the second structure, the opening of the oil passage in communication with the third port of the pressure regulating valve and that of the oil passage in communication with the fifth port thereof which are provided in one member of the valve body are provided so as to overlap both the opening of the source pressure oil passage and that of the drain oil passage which are provided in the other member of the valve body respectively. Therefore, when a hydraulic transmission unit, in which the hydraulic lockup chamber is opened in the hydraulic transmission chamber, is changed to a hydraulic transmission unit in which the hydraulic lockup chamber is provided independently, it is possible, by merely replacing a separator plate, to reverse the relationship between the supplying and discharging of a hydraulic pressure done by an operation of the pressure regulating valve, and thereby adapt the apparatus to a change in the type of lockup clutch of the hydraulic transmission unit. Consequently, according to this structure, only the replacement of a separator plate, which serves the purpose by merely making a change in the position of the communication port thereof, eliminates the need for the valve body, which demands a change of the design of a metal mold therefor when the arrangement of oil passages is changed.
According to the third structure, the opening of the oil passage communicated with the first port and that of the oil passage communicated with the sixth port are provided so as to overlap both the opening of the hydraulic transmission passage and that of the hydraulic lockup passage respectively. Therefore, even when a hydraulic transmission unit in which the hydraulic lockup chamber is provided independently is changed to a hydraulic transmission unit in which the hydraulic lockup chamber is provided non-independently, it is possible, by merely replacing a separator plate, to control a differential pressure of the hydraulic transmission unit set in accordance with an operation of the lockup clutch with respect to that of the pressure regulating valve.
According to the fourth structure, the opening of the oil passage in communication with the first port and that of the oil passage in communication with the sixth port are provided so as to overlap both of the opening of the hydraulic transmission passage and that of the hydraulic lockup passage respectively. Therefore, when a hydraulic transmission unit, in which the hydraulic lockup chamber is provided non-independently, is changed to a hydraulic lockup chamber in which the hydraulic lockup chamber is provided independently, it is possible, by merely replacing a separator plate, to control a differential pressure of the hydraulic transmission unit set in accordance with the operation of the lockup clutch with respect to that of the pressure regulating valve.
According to the fifth structure, the hydraulic pressure of the hydraulic transmission chamber can be controlled by the relay valve, so that a coupling force of the lockup clutch can be increased.
According to the sixth structure, the hydraulic pressure of the hydraulic transmission chamber can be controlled irrespective of the movement of the pressure regulating valve by forming the relay valve separately from the pressure regulating valve.
According to the seventh structure, the valve body can be made compact by forming the relay valve and pressure regulating valve integrally.